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View Full Version : New to WI, lots of questions


FordNut
30-06-2004, 03:55 AM
Background: I currently have a 2003 Mercury Marauder, which has the same engine as the '03-'04 Mach1 (basically the same as the'01 Cobra). It is a 4.6L dohc 32 valve V8 with 10:1 CR. Currently I have virtually all mods possible on a NA car except a bigger MAF sensor, which is soon to be installed. It is currently putting out 297hp to the rear wheels. I plan to supercharge next year with a ProCharger D1SC and air-air intercooler. Most people using blowers on the Marauder are running 8-10 psi boost with a air-water intercooler and making about 450 RWHP. I've seen some of the Mustang guys are experimenting with WI these days so I know it can be done on these engines. Everybody on the Marauder forums poo-poos the notion of water injection but I'm not afraid to explore new ideas. So here is what I understand so far about WI, along with some ideas I have for implementation and some questions.

If possible I would like to get a system that is adequate for the SC application and install it while my car is still NA. I believe the only additional parts I would need are a vacuum switch and nozzles?

Safety interlocks should cut timing and boost if there is no water flowing and should prevent the pump from running if the tank is empty. I have seen a diagram of a pressure relief system posted in these forums which is for a turbo, would something like that work on a blown application? How would it be plumbed? The timing change could be handled by switching to a different program on my chip. I have a flip-chip which currently has two programs (a 93 and a 91 octane file) but it could be reflashed so that one program has timing for WI and the other without. Is there a signal available from the Aquamist controller to handle this switching?

Is the Aquamist pump compatible with all 3 commonly used alcohols (isopropyl, ethyl, methyl)? If not, what pump would be recommended that is compatible? And would it work with the Aquamist controller? Does it have adequate capacity for approximately 500 RWHP (~600 FWHP), or would dual pumps be required? Are accumulators commonly needed or do the pumps just run deadheaded?

It seems like the more accurate control method is to use the fuel injector duty cycle to control the water injection rather than just sizing the nozzle for max demand. What are the negative aspects of this method, if any?

Location of the injector(s) should be between the intercooler and the throttle body, but does it make any difference whether it is close to the throttle body or far away from it?

Would this application warrant multiple water injector nozzles? If so, how should they be controlled and where should they be located?

Does anybody have stainless steel nozzles?

My new MAF sensor has a separate IAT sensor (the OEM one has both sensors incorporated into the MAF itself) so I could locate the IAT sensor upstream, downstream, outside, or basically anywhere. Would it make sense to have it downstream from the nozzle(s) or does it matter? Surely it should be after the intercooler, shouldn't it?

Tuning is a big question mark. My tuner has never worked with WI. From what I understand, the process should be to tune the AFR for about 12.5:1 (that is what we have been setting the Marauders to anyway) without WI, then just leave it alone. The timing will be adjusted differently based on whether WI is on or off. So my programmer would tune for optimum performance at reduced boost (maybe 8-10 psi), without WI and then tune again for optimum performance with high boost (maybe 12-15 psi) with WI. This portion of the tuning should only modify the timing and not change the fuel tables? Burn those two programs into my chip and setup the WI controller to switch between the two programs. Does this make sense or am I way off in left field? And what kind of special tuning can be done to pick up a few extra ponies with the WI while I am still NA?

The Aquamist system is the only one I have seen that has the level of controls to make this happen. Any suggestions on what model and additional parts I should get?

Thanks for any help or advice for this WI newbie!

Charged Performance
04-07-2004, 05:22 PM
For the NA system design yes a vacuum switch set to turn on when the vacuum is less than the level you want it to turn on. If the nozzles are after the throttle plate you would also want a check valve.

For system condition checking Aquamist's DDS 2 would be the best bet it would send a binary signal for too low or too high a water flow. Too low would indicate a blockage somewhere or a leak before the DDS2. Too high would be a leak after the DDS2. A tank level switch should be easy to employ both for disengaging the water injection system and signaling the lack of WI. The Aquamist race pump will not self prime and is not tolerant of running dry.

Aquamist is not highly alcohol tolerant. The only alcohol that it can tolerate is methanol and then only up to a 50% concentration. All other alcohols in any usefull concentration would cause the pump seals to swell. Aquamist components can be adapted to be used with other pumps but some circuitry may need to be altered.

It is hard to equate power to the exact water flow, too many variables about how that power is being generated (displacement or induction or fueling, etc). The pump's flow by itself would be 300cc/min of water. I would expect you to be using more than this. A priming pump at the water source and an accumulator should bring the flow and pressures you would need though.

The location of the nozzles can be any number of places, betwee the IC and the TB is common, but not required. Some are before the IC, some are after the TB. With SC some are before the charger some are after. It's location is dependent on both the logisitics of the intake system and also in the manner that WI is being sought to assist with detonation control.

Yes you probably would want two nozzles. The can be controlled by a single controller with a tee after the controller to each nozzle.

I would think that someone has SS nozzles but I am not aware of any.

The location of the IAT is dependent on your desires and whether or not it would be tolerant of the mist. For instance if you want to know the dry IAT for tuning or WI control or if it is not tolerant of the mist then it would be before the nozzle. If you want it to control the tune based on the wet IAT then it would go after the nozzle. That way if there is not enough water or the water is not cooling enough the tune can adjust for the IAT level getting to the cylinder. However, the IAT wouldn't be able to account for whether there is actually water in the cylinder charge or not the tune should assume it is there and use the DDS2 to tell it if it isn't getting there.

If the engines are able to be tuned det free to 12.5 AFR throughout their power range without water injection - water injection would not be needed in that condition. Leave it be. Water injection is for detonation control to get rid of overly rich tuning. At 12.5 AFR it isn't overly rich and if there is no detonation it wouldn't be needed. The exception would be if the 12.5 AFR is achieved by running overly retarded timing. If the performance of the tune would be improved by advancing the timing, but without water injection the timing can not be advanced due to det issues then a small amount of water (10% water to fuel) can be used to permit the timing to be advanced to the more powerful levels.

Definitely get a water injection off tune first. If water injection is going to only be used for cooling higher boost from that base tune. You will need a lot less water and only need to adjust timing. If you want to get back to 12.5 AFR with the higher boost you will need more water and the fueling would have to be adjusted as well.

From the sounds of it the system 2d with a DDS2 would be right for you. Though you still need to consider whether or not you would want an alternative pump.